Help please! Head gasket? Weird symptoms and lack thereof

[bdrlgion]

Alright, so this is a weird one for me.

97’ SR5 6cyl, 260k mi. Generally good shape, has always run like a top. All minor maintenance done religiously, and timing belt/etc about 20k miles ago.

So about two weeks ago I noticed Big Red started shuttering upon cold start. This was brief and went away after 15 or so seconds. After a few days of that I got the bright idea to check the coolant level, and the reservoir was empty. Added maybe 16oz or so and she was full again. It never overheated, before, during or since.

She hasn’t leaked any coolant since my religious monitoring about a week ago, and it doesn’t shutter upon cold start any more.

No coolant in oil and vice versa. No visible coolant leaks anywhere.

Compression test is 175, then between 190-200 on the others.

Exhaust gas test is good - fluid stayed blue and tried multiple times this week.

Radiator pressure test - went from 13psi to about 10psi in about an hour

A bit more steam from the exhaust than normal, I think, but it’s damn cold in Seattle this month. Also can’t really smell coolant in fumes since I’ve got smellblind post-Covid (damn you, Dewey Cox).

Did a borescope on 5 of the 6 cyls, everything looked ok, no fluid. Couldn’t get to the sixth since plug was seized at the time, and I had return scope to buddy that afternoon. It’s since been freed and that cylinder was one that compression tested around 200.

I’d hate to take it into a shop who’s going to be eager to throw a HG job at it, if that’s not actually the issue. But if it is, I’m ok with that.

Sooooo…what am I missing here? What else should I investigate? The shutters/coolant loss make me think it can’t be anything but the dreaded HG, but I’m absolutely a novice.

 

[thegipper]

Long story short, I had a suspected bad head gasket. I did all of the tests you did (exhaust test with the dye, compression test, bore scope etc) and nothing was conclusive.

I eventually did a leak down test as suggested by others on here. Once I pressurized cyclinder number 3, I had air bubbles coming out of the top of the radiator. Case closed, bad head gasket or cracked head.

Moral of the story, a leak down test is the gold standard in determining if you have a bad head gasket. It also can be used to diagnose other problems as well. I suggest you perform the leak down test. It is the most reliable way to get a definitive answer.

That coolant you lost went somewhere, either it leaked (maybe slowly) or it was burnt in the engine.

Good luck!

 

[JohnMc]

Did all 6 plugs look the same?

 

[bdrlgion]

Yes.

 

[phattyduck]

That coolant you lost went somewhere, either it leaked (maybe slowly) or it was burnt in the engine.

Good luck!

Something as simple as a bad radiator cap would cause that... My sister had my 4Runner before me - when I got it from her, it was a GALLON low on coolant. Filled it up, no leaks or loses since then other than a little spitting from the radiator cap that stopped when I replaced it with a new OEM one. So, don't discount the simple things.

This could be a bad injector, TPS, MAF, etc. too.

-Charlie

 

[bdrlgion]

Something as simple as a bad radiator cap would cause that... My sister had my 4Runner before me - when I got it from her, it was a GALLON low on coolant. Filled it up, no leaks or loses since then other than a little spitting from the radiator cap that stopped when I replaced it with a new OEM one. So, don't discount the simple things.

This could be a bad injector, TPS, MAF, etc. too.

-Charlie

Hmmm. No evidence of coolant loss near/under the radiator cap.

How could a bad injector, MAF cause coolant loss?

 

[Daryl Elmore]

Mine had the same symptoms and it was a cracked head. It would blow extra smoke on cold starts but then clear up with a little rough idle for 15 sec's or so. There were 2 small cracks between the valves on cyl 4. It would let some coolant seep into the cylinder when cold but then as the head heated up the cracks would seal up and it would run fine.

 

[bdrlgion]

Mine had the same symptoms and it was a cracked head. It would blow extra smoke on cold starts but then clear up with a little rough idle for 15 sec's or so. There were 2 small cracks between the valves on cyl 4. It would let some coolant seep into the cylinder when cold but then as the head heated up the cracks would seal up and it would run fine.

Wouldn't a borescope show coolant on cylinders after letting it rest overnight? I did that and everything was bone dry.

 

[JohnMc]

If you don't see a suspiciously cleaner looking plug, it's not likely to be a HG issue. Getting steam cleaned usually won't go unnoticed. Unless all 6 are so new they're all really clean.

I'd guess you should probably just wait until the symptoms become a little more obvious?

 

[spartacus]

CLeaning the maf and replacing the pcv valve wouldn't hurt.

 

[Daryl Elmore]

Wouldn't a borescope show coolant on cylinders after letting it rest overnight? I did that and everything was bone dry.

Unless it gets pushed in at startup when the cooling system gets pressurized? the piston in that hole was also noticeably cleaner than the others.

 

[bdrlgion]

Would a bad heater control valve result in a loss of pressure during a test? I went from 13psi to 10psi when i hooked a gauge up to the radiator, in about an hour. AND I noticed a little bit of pink crud around the heater control valve.

 

[deejay35]

I had a very small coolant leak and couldn't figure out where it was going. Then, one day on the freeway, my heater valve gave out. The entire nipple that the driver's side hose was connected to, completely broke off. I had to get towed back home. It wouldn't be a bad idea to check the hose connections on that OEM *plastic* heater valve.

My 98 had about 225k when this happened a couple of months ago.

 

[NinetySeven]

Somewhat related, I'm having my 1997 4Runner SR5 engine rebuilt due to very similar symptoms. Last time I experienced white smoke from my tailpipe, a cracked cylinder head was to blame.

I've decided to just bite the bullet and do a full rebuild so that I can go another 250K!

Here are photos of the work so far. I'll be honest -- I'm not terribly knowledgeable. What do you guys see here?

PICS: https://imgur.com/a/GjoHeu0

 

[mtbtim]

I will echo what others have already stated. A rough start in the morning and an unexplained coolant loss is indicative of a bad head gasket or cracked head. Knowing this engines, it's a cracked head.

Coolant doesn't magically disappear. There are places coolant leaks stay hidden, like in the valley between the heads, but for the most part, you'll see coolant making it's way down to the ground letting you know you have a leak somewhere.

The combustion gas tools are a joke. I had 100% confirmed coolant was getting into the #3 cylinder of [MENTION=102606]infamousRNR[/MENTION] 2002 4runner and the combustion gas detector did not confirm the issue. I think they are fairly worthless as an accurate tool to diagnose a head gasket or cracked head problem.

I think you should follow the suggestion from others and myself and do a leak down test of all cylinders, but take it one step further and use a cooling system pressure tester in conjunction with the leak down tester. The first video will show you how to properly set up each cylinder for a leak down test. The second video shows a positive finding of a head gasket failure or cracked head using the cooling system pressure tester in conjunction with the leak down tester. Good luck!


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[mtbtim]

Would a bad heater control valve result in a loss of pressure during a test? I went from 13psi to 10psi when i hooked a gauge up to the radiator, in about an hour. AND I noticed a little bit of pink crud around the heater control valve.

If you were losing the pressure at the heater control valve, it would be accompanied by coolant leaking out. Some crusty residue is a sign there is some seepage though.

You need to do that same cooling system pressure test and then look into the cylinders with your borescope camera looking for signs of coolant pooling on top of the pistons. I wouldn't do it for just one hour. Keep topping off the pressure for several hours and then go in with your borescope camera. I'm guessing you're going to find coolant on one of the pistons. I'd check the #3 cylinder first. That seems to be a common failure point on these engines.